The present invention relates to a process for producing isocoumarin-3-yl-acetic acid derivatives and to synthetic intermediates to be used in the process.
It is known that the isocoumarin-3-yl-acetic acid derivatives, for example, a compound represented by a formula: 
are effective for preventing and curing an abnormal immunoregulating action or a disease following angiogenesis (International Publication WO97/48693). According to this international publication pamphlet, the above compound is produced from 8-hydroxy-3-methyl-6-methoxy-isocoumarin via several steps. This is an excellent process in terms of that any of the respective steps in this process proceeds at a good yield but can not necessarily provide isocoumarin-3-yl-acetic acid derivatives having various substituents at a good efficacy.
Accordingly, there still exists a need for a process in which an isocoumarin-3-yl-acetic acid derivatives can efficiently be produced and particularly a process for producing the above derivative which can have various substituents in a 2-position of a acetic acid chain capable of exerting a strong effect on a biological activity.
The present inventors have found that a cyclocondensation reaction of some kind of a homophthalic acid derivative with some kind of a malonic acid derivative is allowed to proceed by one pot, whereby a wide variety of isocoumarin-3-yl-acetic acid derivatives can efficiently be produced. Further, we have found as well that in the reaction described above, a corresponding xcex2-oxocarboxylic acid derivative before the cyclocondensation reaction can efficiently be obtained by selecting the reaction conditions. The present invention is based on such knowledge as described above.
Hence, according to the present invention, provided is the following process, that is, a process for producing isocoumarin-3-yl-acetic acid derivatives which are represented by the following formula (I): 
(wherein R represents a hydrogen atom, a non-substituted or substituted alkyl group, a non-substituted or substituted alkenyl group, a non-substituted or substituted alkynyl group, a non-substituted or substituted alkoxyl group, a protected amino group, a hydroxyl group or a protected hydroxyl group; Ra represents a hydrogen atom or a protecting group for a carboxyl group; Rb represents a hydrogen atom or a protecting group for a hydroxyl group; and Rc represents a non-substituted or substituted lower alkyl group), the above process comprising:
reacting a homophthalic acid derivative represented by the following formula (III): 
(wherein Rc represents a non-substituted or substituted alkyl group; R1 represents a hydrogen atom or a protecting group for a carboxyl group; and R2 represents a hydrogen atom or protecting group for a hydroxyl group) with a malonic acid derivative represented by the following formula (IV): 
(wherein R is synonymous with that defined for formula (I); R3 represents a protecting group for a carboxyl group; and X represents a xe2x80x94OM group (wherein M is alkaline metal or alkaline earth metal), chlorine or bromine) in an inert organic solvent in the presence of a condensing agent, wherein a xcex2-oxocarboxylic acid derivative represented by the following formula (II) in optionally formed during the above reaction: 
(wherein R and Rc are as defined for formula (I), and R1, R2 and R3 are as defined for formulas (III) and (IV)); and the protecting groups for a hydroxyl group and/or a carboxyl group are be subjected to an elimination reaction, if necessary.
On the other hand, both of the xcex2-oxocarboxylic acid derivative represented by formula (II) described above and a half ester (monoester) of the homophthalic acid derivative in which R1 in formulas (III) described above represents a protecting group for a carboxyl group are, to knowledge of the present inventors, novel compounds which are not described in conventional technical documents. Hence, according to the present invention, these novel compounds are provided.
The definitions of the respective groups specifying the compounds represented by the respective formulas related to the present invention shall specifically be explained below.
The xe2x80x9clower alkyl groupxe2x80x9d means a linear or branched, saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms and includes, for example, methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isoamyl and n-hexyl. The preferred alkyl group is the group having four or less carbon atoms. As described later, the examples described above can be applied in the present specification including the case where the lower alkyl group takes a share in a part of some group. Substituents in the case where these alkyl groups are substituted include halogens, a cyclo-alkyl group having 3 to 7 carbon atoms, a lower alkyl group having at least one carbon atom, an aryl group (for example, phenyl and naphthyl) which may be substituted with halogens and nitro, a lower alkoxy group, a lower alkylthio group and a mono- or di-lower alkyl-substituted amino group. At least one of these substituents can be present. Halogens mean fluorine, chlorine, bromine and iodine, but halogens in the substituents described above are preferably fluorine and chlorine. The lower alkyl groups in the lower alkoxy group, the lower alkylthio group and the lower alkyl-substituted amino group comply with the definition of the xe2x80x9clower alkyl groupxe2x80x9d described above (hereinafter, this is common through the whole present specification). Specific examples of the substituted alkyl group include fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, dichloromethyl, cyclopropylmethyl, cyclopentylmethyl, 1-cyclopropylethyl, benzyl, benzhydryl, methoxymethyl, i-propoxymethyl, methylthiomethyl, methylaminomethyl, dimethylaminomethyl, dimethylaminoethyl and diethylaminomethyl.
The xe2x80x9clower alkenyl groupxe2x80x9d means a linear or branched aliphatic hydrocarbon group having 2 to 6 carbon atoms and a carbon-carbon double bond and includes, for example, ethenyl, propenyl, n-butenyl, i-butenyl, 3-methylbut-2-enyl and n-heptenyl. Substituents in the case where these lower alkenyl groups are substituted can be synonymous with the substituents in the xe2x80x9clower alkyl groupxe2x80x9d described above. Further, a substitution mode in the substituents applies correspondingly to the case of the lower alkyl group described above.
The xe2x80x9clower alkynyl groupxe2x80x9d means a linear or branched aliphatic hydrocarbon group having 2 to 6 carbon atoms and a carbon-carbon triple bond and includes, for example, ethynyl, propynyl, n-butynyl, i-butynyl, 3-methylbut-2-ynyl and n-pentynyl. Substituents in the case where these lower alkynyl groups are substituted can be synonymous with the substituents in the xe2x80x9clower alkyl groupxe2x80x9d described above. Further, a substitution mode in the substituents applies correspondingly to the case of the lower alkyl group described above.
The xe2x80x9clower alkoxy groupxe2x80x9d in the definition of the xe2x80x9cRxe2x80x9d group is common to the lower alkoxy groups given as the examples of the substituents for the lower alkyl group described above and includes, for example, methoxy, ethoxy, n-propoxy, i-propoxy, n-botoxy, sec-butoxy, tert-butoxy and n-pentyloxy. Substituents in the case where these lower alkoxy groups are substituted can be synonymous with the substituents in the xe2x80x9clower alkyl groupxe2x80x9d described above. Specific examples of the substituted lower alkoxy group include fluoromethoxy, difluoromethoxy, trifluoromethoxy, cyclopropylmethoxy, benzyloxy, methoxymethoxy, ethoxymethoxy, ethoxyethoxy, dimethylaminomethoxy and dimethylaminoethoxy.
A protecting group in the xe2x80x9cprotected amino groupxe2x80x9d, the xe2x80x9cprotecting group for a hydroxyl groupxe2x80x9d and the xe2x80x9cprotecting group for a carboxyl groupxe2x80x9d mean groups having a function for blocking or inhibiting a reactivity of the respective corresponding functional groups in order to avoid or reduce undesirable side reactions in the reaction according to the present invention. Further, in the present invention, groups which allow the corresponding compounds to be usable as a pro-drug while these protecting groups are present can be included as well in the protecting groups. These protecting groups can be selected from those described in, for example, xe2x80x9cProtective groups in Organic Chemistryxe2x80x9d, John Wiley and Sons, 1991, which are usually used by a person having an average skill in the art.
Among them, the protecting group in the preferred xe2x80x9cprotected amino groupxe2x80x9d includes a lower alkanoyl group (for example, acetyl, propionyl and the like), an arylcarbonyl group (for example, benzoyl and the like), a silyl group (for example, tert-butyldimethylsilyl, tert-butyldiphenylsilyl and the like), an aryl- or lower alkyl-oxy-carbonyl group (for example, benzyloxycarbonyl, tert-butoxycarbonyl and the like) and a lower alkylsulfonyl or arylsulfonyl group (for example, mesyl, tosyl and the like). The xe2x80x9cprotecting group for a hydroxyl groupxe2x80x9d includes a lower alkyl group in addition to the preceding protecting groups for an amino group.
The xe2x80x9cprotecting group for a carboxyl groupxe2x80x9d includes a lower alkyl group and a phenyl-substituted lower alkyl group which may be substituted if necessary (for example, benzyl, benzhydryl, trityl, p-nitrobenzyl and the like).
The protecting group in which the compound in the case where Rb represents the protecting group for a hydroxyl group in formula (I) can be a pro-drug includes the case where Rb is selected from such residues in which a hydroxyl group and a remaining carboxyl group are protected in a certain case that xe2x80x94ORb can finally form acetic acid ester, propionic acid ester, succinic acid ester, fumaric acid ester, maleic acid ester, lactic acid ester, tartaric acid ester or malonic acid ester.
As described above, the isocoumarin-3-yl-acetic acid derivative of formula (I) which is effective for preventing and curing an abnormal immunoregulating action or a disease following angiogenesis can advantageously be produced by a one pot reaction of the malonic acid derivative of formula (IV) with the homophthalic acid derivative of formula (III) which passes, if necessary, through the formation of the compound of formula (II) (or called a xcex2-oxocarboxylic acid derivative) which is novel. On the other hand, according to the present invention, provided as well is a process for producing the compound of formula (I) obtained by a cyclization reaction from the compound of formula (II) which may be obtained by any production process.
Synthetic examples of the compound of formula (I) developed by the present inventors including the typical production examples of the compound of formula (III) shall specifically be explained while referring to the following scheme. 
In the scheme described above, R, Rc, R1, R2, R3 and M are as defined above; R1-1 is a protecting group for a carboxyl group; THF is tetrahydrofuran; DMF is dimethylformamide; Et is ethyl; and t-Bu is tert-butyl. The fifth step shown in a brancket may be independently carried out, if necessary (hereinafter, the same shall apply).
The following 1""st step can be adopted as an alternative method for the first step described above: 
Synthetic Scheme B (Another Process for Producing the Compound in which R1 of Formula (III) is a Hydrogen Atom and Using the Above Compound 
In the scheme described above, R, Rc, R2 and R3 are as defined above, and X is a xe2x80x94OM group (wherein M is as defined above), Cl or Br.
Explanation on Synthetic Scheme A
A part of the compounds represented by formula (VI) is publicly known according to M. Yamaguchi et. al., J. Org. Chem., 55, 1611 (1990), R. N. Hurd et. al., J. Med. Chem., 16, 543 (1973), W. R. Rough et. al., J. Org. Chem., 57, 6822 (1992) and F. M. Hauser et. al., J. Org. Chem., 42, 4155 (1977). According to M. Yamaguchi et. al., a compound in which R1-1 in formula (VI) is tert-butyl is obtained starting from ethyl 3-hydroxyglutarate, and according to R. N. Hurd et. al, a compound in which R1-1 in formula (VI) is methyl is obtained via a self-condensation and then the decarboxylation of a compound of formula (VII).
It is a matter of course that the compound of formula (VI) obtained by any method can be used in the preceding synthetic scheme according to the present invention, but according to the present invention, the compound of formula (VI) is preferably produced according to the 1""st step or 1""st step in the synthetic scheme described above. In this step, the intended compound of formula (VI) can be obtained by one step by reacting the acetonedicarboxylic acid ester of formula (VII) with the diketene of formula (VIII) in a suitable inert organic solvent (for example, THF, dioxane, dimethylsulfoxide (DMSO), DMF, acetonitrile and toluene) in the presence of a base, for example, sodium hydride, sodium methoxide, potassium tert-butoxide and calcium oxide. Usually, this step can be carried out by stirring a mixture of an acetonedicarboxylic acid ester and a base at 0 to 40xc2x0 C. for several minutes to several ten minutes, then cooling the reaction mixture down to 10xc2x0 C. or lower, adding diketene to further stir and react them at the same temperature for 0.5 to 5 hours and, if necessary, further carrying out the reaction at 20 to 70xc2x0 C. A use proportion of the acetonedicarboxylic acid ester to the diketene is 1:3 to 2:1, preferably almost equimolar equivalent. A use amount of the base is a molar amount slightly exceeding that of the former.
The 1""st step is carried out in a single step by subjecting an acetonedicarboxylic acid ester represented by Formula (VII) to self condensation and decarboxylation in a suitable inert organic solvent (for example, THF, 1,4-dioxane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, DMF and DMSO) in the presence of an inorganic salt (for example, alkaline metal or alkaline earth metal halides such as lithium chloride, lithium bromide, lithium iodide, lithium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium fluoride, potassium chloride, potassium bromide, potassium iodide, potassium fluoride and magnesium chloride; and transition metal halides such as zinc chloride and copper chloride).
Usually, this step can be carried out by dissolving an acetonedicarboxylic acid ester in an organic solvent, adding an alkaline metal salt and stirring and reacting at 50 to 150xc2x0 C. (preferably about 130xc2x0 C.) for 1 to 30 hours (preferably about 3 to 23 hours). Provided that when THF or 1,4-dioxane is used as the solvent, the reaction is carried out on a refluxing condition.
A use proportion of the acetonedicarboxylic acid ester to the alkaline metal salt is 1:0.1 to 0.1:1, preferably 1:0.1 to 1:1.5.
The production process for the compound of Formula (VI) shown in the 1st step and the 1""st step was described in a conventional technical literature as long as the present inventors investigated.
The compound of formula (VI) thus formed can be obtained by refining the reaction mixture of the compound of formula (VI) thus formed by extraction with an organic solvent such as ethyl acetate and, if necessary, chromatography using silica gel.
The compound of formula (V) having a form in which the hydroxyl group of the compound of formula (VI) is protected in the second step is partially publicly known as well according to M. Yamaguchi et. al. Hydroxyl groups in a 2-position and a 4-position of the compound of formula (VI) are etherified at the same time or in order one after the other, or the hydroxyl group in the 4-position is etherified and then the hydroxyl group in the 2-position is esterified, or etherification and esterification can be carried out in a reverse order. These etherification and esterification can be carried out using suitable reactants corresponding to Rc and R2 according to publicly known methods.
Further, the compound of Formula (V) can be obtained as well by esterifying two carboxyl groups of the compound of Formula (III-2) which shall be described later.
The compound of formula (V) thus obtained is subjected to a partial hydrolytic reaction of a homophthalic acid diester in the third step and converted into a half-ester (or a homophthalic acid monoester) of formula (III-1) in which an acetic acid ester part (an alkylcarboxylic acid ester group) is hydrolyzed into a free carboxyl group. Even when two R1-1""s in the compound of formula (V) are the same group, the partial hydrolysis described above goes on efficiently, but respective R1-1""s can be selected as well so that the alkyl carboxylic acid ester group is hydrolyzed more easily than the aryl carboxylic acid ester group. A combination thereof includes, for example, a case where R1-1 in the former is methyl, ethyl, propyl or isopropyl and R1-1 in the latter is benzyl. This hydrolytic reaction condition is under the control of the kind of R1-1 selected, and the hydrolysis is preferably carried out usually in a water base solution in the presence of a base (for example, NaOH, KOH, Ba(OH)2 and LiOH).
The half-ester of formula (III-1) can be refined by extraction with an organic solvent and, if necessary, chromatography using silica gel. The half-ester (or homophthalic acid monoester) of formula (111-1) is not described as well in conventional technical documents.
In the fourth step, the homophthalic acid monoester described above is reacted with the malonic acid derivative of formula (IV-1) in an inert organic solvent. Any solvents can be used as long as they do not exert an adverse effect on the present reaction. Usually, THF, DMF, dioxane or acetonitrile is preferably used. The malonic acid monoester salt of formula (IV-1) (M in formula (IV-1) is an alkaline metal such as potassium and sodium or an alkaline earth metal such as calcium and magnesium) is stirred in a solvent at 0 to 40xc2x0 C., suitably a room temperature (usually 20 to 30xc2x0 C.) for 0.5 to 5 hours in the presence of a condensing agent, particularly a base (for example, trtiethylamine, diisopropylamine, pyridine and lutidine) and an additive (for example, MgCl2, MgBR2, Mg and MgO) to prepare a reaction solution. Separately, the compound of formula (III-1) is stirred preferably in the solvent used for preparing the reaction solution described above at 0 to 40xc2x0 C., suitably a room temperature for 0.5 to 5 hours in the coexistence of a condensing agent (for example, carbonyldiimidazole and the like) to prepare another reaction solution. Both reaction solutions thus prepared are mixed at 0 to 40xc2x0 C. and then, if necessary, heated while stirring. The stirring time can be determined by tracing a consumed level of the starting material and/or a kind or a level of a newly resulting product on a thin layer chromatogram. Usually, it is about 4 to 20 hours in stirring at a room or elevated temperature. Thus, the compound of formula (I-1) can be produced by one pot, but the compound of formula (II) formed in the middle of the reaction may be separated from the reaction mixture to carry out separately a cyclization reaction to thereby produce the compound of formula (I-1).
The compound of formula (IV-1) used for the raw material is a compound which is almost publicly known in documents, and a novel compound can be produced in the same manner as in known compounds or from known compounds.
In the reaction described above, the compound of formula (III-1) and the compound of formula (IV-1) are used usually in a proportion of 1:1 molar equivalent to 1:4 molar equivalent. The optimum concentrations of these compounds in the reaction solution can be determined by a person having an average skill in the art by carrying out simple experiments.
The cyclization reaction of the compound of formula (II) can be carried out by stirring the reaction solution in a suitable inert organic solvent (for example, THF, DMF, dimethoxyethane, dioxane, acetonitrile and toluene) at 0 to 40xc2x0 C., suitably a room temperature in the presence of a base (for example, amines such as triethylamine, diisopropylamine, pyridine and lutidine, or alkaline metal alcoholate such as potassium t-butoxide and sodium methoxide or sodium hydride). This reaction causes an elimination of R2 and R3 in a certain case in addition to the cyclization described above. Thus, the compound of formula (I-1) or (I)xe2x80x2 can be obtained.
When the mixture of the preparation of the compound of formula (IV-1) described above and the preparation of the compound of formula (III-1) is reacted by one pot, the reaction is carried out preferably by stirring the mixture for a fixed time and the further elevating the temperature. In this case, the fixed time described above is decided by analyzing an aliquot of the reaction solution with the passage of time by means of a thin layer chromatography to determine the extent of a dissipation in spots which are considered to correspond to the compound of formula (II). The reaction solution is heated after the compound of formula (II) of exceeding almost 50%, preferably almost 80% or more in terms of the extent of dissipation is consumed. The temperature can be elevated up to the boiling point of the solvent used.
In this one pot reaction, organic amines, for example, triethylamine and diisopropylamine are suitably used for the base.
Explanation on Synthetic Scheme B
The compound of formula (IX) can be converted into the compound of formula (III) according to, for example, F. M. Hauser et. al., J. Org. Chem., 42, 4155 (1977) described above in which the conversion of a part of the compounds is described, or a revised method thereof.
To be typical, a base (for example, diisopropylamine and diethylamine) is allowed to coexist with organic lithium (for example, t-butyllithium, n-butyllithium and the like) in an inert solvent (for example, tetrahydrofuran (THF), dimethylformamide (DMF) and dimethylsulfoxide (DMSO)) to react the compound of formula (IX) with di-lower alkyl carbonate (for example, dimethyl carbonate). Usually, this reaction can be carried out by stirring at 0 to xe2x88x9280xc2x0 C., preferably xe2x88x9270 to xe2x88x9275xc2x0 C. for one hour. Water is added to the reaction solution to further continue the reaction at a room temperature (20 to 30xc2x0 C.) while stirring, whereby the intended homophthalic acid derivative is formed.
The use proportions of the respective raw materials can suitably be selected considering a profitability of the compounds used. Usually, di-lower alkyl carbonate can be used in an amount of equimole or twice mole based on the compound of formula (IX). The preferred use proportions of the other raw materials shall be able to be selected in the respective cases with reference to Production Example 1 which shall be described later.
The compound of formula (111-2) thus formed can be separated from the reaction mixture by making use of an extraction method using an organic solvent such as ethyl acetate or, if necessary, a chromatography using silica gel.
The reaction of the compound of formula (111-2) with the compound of formula (IV) can be completed by stirring them in an inert solvent (for example, dichloromethane, chloroform and the like) at 0 to 40xc2x0 C., preferably a room temperature usually for 0.5 to 3 hours, preferably 2 to 3 hours in the presence of a base (for example, triethylamine, diisopropylethylamine, pyridine and the like). The preferred use proportions of the respective reactants used in the reaction described above can be settled as well with reference to the production examples described later. The respective protecting groups of the product thus obtained can be eliminated, if necessary, by a known elimination reaction, whereby it can be converted into the intended bioactive substance of formula (I).
The o-orsellinic acid derivative of formula (IX) can be produced etherifying or, if necessary, esterifying the hydroxyl groups in the 4- and/or 6-positions of o-orsellinic acid according to a known method.
Hence, according to this method, the intended compound can be produced from readily available starting materials at a very high yield by less steps.
The compound of formula (I-1) or (I)xe2x80x2 thus formed are subjected, if necessary, to hydrolysis of the respective protecting groups to obtain particularly a compound in which R2 and R3 are selectively eliminated. Such hydrolytic reaction can be carried out by a publicly known method.
In particular, when R2 in formula (I-1) is a lower alkyl group, it is relatively difficult to selectively eliminate only the above lower alkyl group while allowing a Rc group to remain, but the reaction can suitably be allowed to proceed according to the following method. That is, typical examples of such elimination method include, for example, a method using boron tribromide and aluminum chloride which is described in xe2x80x9cProtective groups in Organic Chemistryxe2x80x9d, John Wiley and Sons, 1991 and a method using magnesium iodide reported relatively in recent years, which is described in Anthony G. et. al., Chem. Commun., 809 (1998).
However, the reaction is drastic in the former method, so that a little elimination of Rc is caused or an unfavorable effect is exerted on the other parts in a certain case. On the other hand, the above lower alkyl group can be eliminated at a good selectivity in the latter method, but magnesium iodide used is expensive, and therefore it is not suited to production in a large quantity. Accordingly, a method which can be carried out at a lower cost has so far been expected.
The present inventors have found that when R2 in formula (I-1) is a lower alkyl group, a deprotecting reaction in the 8-position proceeds quantitatively by carrying out the reaction of the compound of formula (I-1) in a suitable inert solvent (for example, THF, dioxane, acetonitrile, toluene and the like) containing alkaline metal iodide (for example, potassium iodide, sodium iodide and lithium iodide) and magnesium halide (for example, magnesium fluoride, magnesium chloride and magnesium bromide, preferably magnesium chloride) at 20 to 100xc2x0 C., preferably 60 to 80xc2x0 C. Subsequently, the protecting group R3 is eliminated by a known hydrolytic reaction, whereby the compound of formula (I) in which R2 and R3 in formula (I-1) are deblocked can be obtained. Hence, according to the present invention, provided is the process for producing the compound of formula (I) including the step for selectively eliminating the lower alkyl group of the compound of formula (I-1) in which R2 is a lower alkyl group. In this process, alkaline metal iodide and magnesium halide are used preferably in a range of about 1:2 to 2:1 in terms of a molar ratio, but it shall not be restricted thereto. A use proportion of magnesium halide to the compound of formula (I-1) can be 0.1 to 3 times in terms of a molar equivalent.
Included in the compound of formula (I) thus obtained are 2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzopyran-3-yl)propionic acid described in WO97/48693 and other novel compounds, and it is anticipated that the novel compounds have a biological activity which is the same as or equivalent to that of the above propionic acid, so that they shall be efficient for preventing and curing an abnormal immunoregulating action or a disease following angiogenesis. A preparation used for preventing and curing the above disease can be prepared as well in the same manner as in the above propionic acid.